1. Field of the Invention
This invention relates to a method of automatically detecting a position of a picture frame and stopping the frame in accordance with information regarding a size of an original film such as a negative film, the method being also capable of obtaining an exposure value and correction value of the negative film.
2. Description of the Prior Art
With a photographic printer, in order to suitably print a framed picture of an original film on a photographic printing film, it is necessary to accurately position the picture frame of the original film on an optical frame. This positioning of the picture frame was done in a prior art technique by detecting the position of a notch provided on the side of the original film by utilizing an optical sensor. However, this prior art technique involves a problem in the determination of an accurate positional correspondence between the notch and the picture frame when the notch is provided, and the solution of such a problem is difficult. In another prior art method, the picture frames are positioned by always feeding the frames by a predetermined distance with respect to the original film, but this method also has a problem in that the amount of positional shifts of the picture frames during the continuous frame feeding are increasingly accummulated, thus preventing the picture frames from accurately being fed. Furthermore, in the other prior art technique, there has been proposed a method in which optical sensors, such, as photodiodes, are arranged in conformity with the shapes of the frames of the original film and the positions of the frames are determined by the detected conditions of the photodiodes. However, this prior art technique also includes a problem in that a control algorithm for controlling the photodiodes, for example, is complicated.